Design rules for advanced generation microlithography (i.e., beyond 193 nm immersion lithography and into next generation optics such as e-beam, X-ray, and extreme ultraviolet (EUV) lithography operating at a very short wavelength of 13.4 nm) are trending toward smaller and smaller dimensions, for example, 30 nm and below. In general, depth of focus (DOF) necessarily decreases with higher resolution due to the higher numerical aperture (NA) and therefore resist thickness also decreases to commensurate the smaller and smaller feature sizes. With narrower linewidths and thinner resist films, consistency issues such as line edge roughness (LER) and resolution take on increasing significance limiting the performance and usefulness of photoresists. These phenomena are of interest in the fabrication of semiconductor devices; for example, excessive LER can lead to poor etch and lack of linewidth control in, for example, transistor and gate architecture, potentially causing short circuits and signal delay. Since the radius of gyration of polymeric materials generally used to prepare EUV photoresists is essentially larger than the LER requirement (i.e., less than 3 nm), small, discrete and well defined molecules which when cast form amorphous films, and commonly known as molecular glasses, have been considered as possible candidates for developing EUV photoresist platforms.
Molecular glasses have been used in negative and positive tone resists. U.S. Patent Application Publication No. 2010/0047709 A1 describes a low outgassing resist based on calix[4]arenes prepared from resorcinol or pyrogallol and a substituted aldehyde having, for example, a pendant phenyl or cyclohexyl group, with dissolution control groups attached to the hydroxy groups of the resorcinol/pyrogallol. However, there remains a need for calix[4]arene based photoresists which have improved resolution to meet the stringent requirements for photoresists having desirably high resolution and low LER, and with further improvement in processing stability.